This nonprovisional application claims priority under 35 U.S.C. xc2xa7 119(a) on Patent Application No. 91115816 filed in Taiwan, R.O.C. on Jul. 16, 2002, which is herein incorporated by reference.
1. Field of Invention
The invention pertains to a grating interference device used for photosensitive materials such as optic fibers or planar waveguides. In particular, the invention relates to a resolution adjustable grating interference device with a simple structure and high stability.
2. Related Art
Fiber gratings are often used in optoelectronic devices and have a lot of potential in future applications. Known fiber grating manufacturing methods include the phase mask method (or using other complicated devices) and the two mirror method. The phase mask method has a simpler structure, but it is not adjustable and more expensive. The two mirror method has a more complicate setup, but it is cheaper and adjustable.
To solve the problems in manufacturing and adjustment, there were many proposals in the past. For example, the U.S. Pat. No. 4,148,549 utilizes a multi-mirror structure with an adjustable period and tilt angles. There are three adjustable places and calibration is needed each time an adjustment is made. Therefore, this method is complicated in adjustment. The U.S. Pat. No. 4,807,950 uses a two-mirror structure. The structure is simpler but the adjustment is even harder. The system setup has to be modified every time an adjustment is required. The U.S. Pat. No. 5,309,260 also employs a multi-mirror setup and there are three adjustable places. Similarly, calibration has to be performed each time an adjustment is made. The U.S. Pat. No. 5,881,186 uses a phase grating structure. Although the setup is easier, it is not adjustable. From these references, one sees that there is no grating with a simple structure, an easy setup and an adjustable design.
It is an objective of the invention to provide a grating interference device with adjustable resolution. The disclosed device does not only have a simple structure and high stability, but also a sufficiently precise adjustment accuracy.
The disclosed grating interference device with adjustable resolution contains a beam splitter, two reflectors and a platform. The beam splitter separates an incident laser beam into two outgoing beams. The two reflectors are installed on the pathways of the two outgoing beams, changing their propagating directions toward the platform. The platform is fixed with a photo-sensitive material such as a planar waveguide or an optic fiber. The two reflected beams form an interference pattern on the photo-sensitive material, forming the desired interference grating.
The invention further allows one of the reflectors and the platform to rotate with respect to the beam splitter and the other reflector. This changes the incident angle of the reflected beams, thereby changing the period of the interference grating. Since the period is controlled by rotating the angle, the operation has high stability and accuracy.
On the other hand, one can also change the angle between the platform and one of the reflectors to form a tilt interference grating on the photo-sensitive material.